For years, rotating blades have been used for converting wind and/or water energy into other forms of energy needed to accomplish useful work. For example, classic windmills and wind turbines employ propeller surfaces to engage a wind stream and convert the energy in the wind stream into rotation of a horizontal windmill shaft. These classic windmills, however, have many shortcomings. For example, the propellers or blades of classic windmills are typically facing one direction. If the wind is not blowing in the direction of the propellers, the windmill is not working, and wind energy is not being converted into other forms of energy as desired. Furthermore, regardless of whether optimal wind directionality is achieved, horizontal axis windmills cannot exploit high energy, high velocity winds because such winds can overload the moving blades causing damage or failure. It is necessary to shut down conventional horizontal windmills at wind speeds in excess of 35 mph to avoid these problems. Wind energy increases as the cube of velocity; the cessation of blade operation during high-velocity winds represents a serious disadvantage because this is when the most wind energy is available for conversion.
Vertical axis wind turbines are also available. Although vertical axis turbines address many of the shortcomings of horizontal shaft windmills, they have their own inherent problems. For example, some prior art devices change airflow to the blade areas in undesirable ways, such as the device shown in International Publication No. WO 2009/047679. There, fluid is sucked in through a hollow center of the device's fluid deflectors. A large gap is required between the fluid deflectors in order for the device to operate properly. In particular, the device needs the large gap for a favorable vortex formation, to rotate the blades. Accordingly, such a device may be inefficient, and have a large undesirable height.
Accordingly, an improved prime mover that is efficient and practical is needed.